1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
Priority is claimed on Japanese Patent Application No. 2008-164207, filed Jun. 24, 2008, the content of which is incorporated herein by reference.
2. Description of Related Art
FIG. 14 is the configuration of a related BGA semiconductor device using wire bonding method. In FIG. 14, a semiconductor device 101 includes at least a roughly quadrangular wiring board 2. On one face of the wiring board 2, a plurality of connection pads 3 are fabricated, and a semiconductor chip 6 is secured through, for example, a die-attach film (DAF) 7 that becomes an insulating adhesive. A plurality of electrode pads 8 are formed near the periphery of a top face 6a of the semiconductor chip 6, and are electrically connected to corresponding connection pads 3 of the wiring board 2 by joining them using conductive wires 9 made from, for example, Au or Cu. The one face of the wiring board 2 is then covered with a sealant 10 made from a thermosetting resin such as, for example, epoxy resin, such as to cover the semiconductor chip 6 and the wires 9. Also, solder balls 5 are provided on another face of the wiring board 2 that is on an opposite side to the one face. The solder balls 5 and the connection pads 3 are connected by wiring (not shown) inside the wiring board 2.
Following advancements in electronic devices such as mobile telephones and digital cameras, there are strong demands for smaller and thinner semiconductor devices for mounting, requiring various methods for making them smaller and thinner. As one thinning method, it is important to reduce the thickness of the sealing resin that covers a package top part of a chip and wires for mounting (section H1 in FIG. 14, the thickness from a top face 6a of the semiconductor chip to a top face 10a of the sealant 10). For design purposes, however, if the thickness H1 is made too thin, there is a possibility that variation in the height of the sealing resin and wire bonding caused during mass production will result in exposure of the wires 9, increasing the number of defective products and shortening product lifespan. Therefore, the thickness H1 of the top-part sealing resin (e.g. H1=approximately 0.20 mm) cannot be designed any thinner than a fixed value.
Japanese Unexamined Patent Application, First Publication, No. 1998-189631 discloses one manufacturing method that enables the package top part to be made thinner, wherein one part of a die (movable-part die) is lowered onto the top parts of bonding wires to restrict the wire heights, and in that state a primary resin seal is applied; a secondary resin seal is applied after raising the movable-part die again. In this invention, since only part of the die is lowered and raised again, positional deviation arising when the movable-part die is raised again leave scratches on the package surface, conceivably resulting in external defects and restrictions on marking positions. Also, the movable-part die must be designed and manufactured for each product shape, increasing the cost and the time taken to set the die, etc. Such demerits lead to increased manufacturing cost and manufacturing time, rendering this invention inadequate as a method of thinning.
Further, in a method disclosed in Japanese Unexamined Patent Application, First Publication, No. 2002-299357, after pressing a die against the tip parts of bonding wires and sealing with resin, an insulating coating film (e.g. a film) is pasted over a top-part surface. Conceivable demerits of this method, due to the use a coating film, are reduced reliability (resistance to peeling, moisture, etc.) and the coating film-pasting time (increased operation time), etc.